Power supply module assemblies providing a plurality of control voltages are well known. In many instances, these power supply assemblies are electrically connected in a rack assembly to a programmable logic controller (PLC) that is normally used to control of functions in a manufacturing operation. This programmable logic controller is often of necessity located on the plant floor and thus is subject to considerable abuse.
With the advent of smaller PLCs that are often mounted directly on the controlled device or machine, it becomes increasingly important to have power supply module that is compact in size and still be able to provide several regulated output voltages. Switching voltage regulators have been developed that can generally provide a single output with a variety of protective features and yet require a minimum of external and internal components to meet the size restrictions. Such a regulator is disclosed in the 1989 edition of National Semiconducter's "General Purpose Linear Devices Databook" page 2-51. However, if an additional and isolated output voltage is required, a separate regulator or duplicate circuit must be used for each voltage and a large transformer with multiple secondary windings may also be required. This results in increased size that may not be available on the device that is to be controlled. The present invention eliminates a majority of these extra components without loss of performance and has the potential for multiple output voltages with little additional circuitry.